Full IPCC AR4 report now available

The complete WG1 IPCC 4th Assessment report (AR4) is now available online. It’s missing the index and some supplemental data, but all should be available by May 7.

Over the next few weeks we’ll try and go through the report chapter by chapter, but since this is likely to the key reference for a number of years, we can take a little time to do it properly. Happy reading!

205 Responses to “Full IPCC AR4 report now available”

“We believe there are five simple guidelines for identifying denialist arguments. Most denialist arguments will incorporate more than one of the following tactics: Conspiracy, Selectivity, False Experts, Impossible Expectations/Moving Goalposts, and Argument from Metaphor/violations of informal logic.”

#31 and #36 TROLL. re, “global cooling predicted in 1970s… now they predict global warming … so scientists should not be believed.”

This is covered several times on this site and you know it.

Alastair, these are senseless trolls.

I present hard evidence below, including papers, that show your post is completely ignorant and blatent progaganda…now, where is your evidence?????

There was no scientific consensus on cooling in the 1970s in the scientific journals (not including pop mags, like Time or National Geographic), however there is now a strong consensus that it is warming in the journals. This is the difference between night and day.

This site covers has covered it pretty well as any honest person knows.

“The point to remember, says Connolley, is that predictions of global cooling never approached the kind of widespread scientific consensus that supports the greenhouse effect today. And for good reason: the tools scientists have at their disposal nowâ??vastly more data, incomparably faster computers and infinitely more sophisticated mathematical modelsâ??render any forecasts from 1975 as inoperative as the predictions being made around the same time about the inevitable triumph of communism.” Newsweek

“I should clarify that I’m talking about predictions in the scientific press. There were some regrettable things published in the popular press (e.g. Newsweek; though National Geographic did better). But we’re only responsible for the scientific press. If you want to look at an analysis of various papers that mention the subject, then tryhttp://www.wmconnolley.org.uk/sci/iceage/.”

RE #29, Walt, you may be interested in NATURAL CAPITALISM by Paul Hawkin and Amory Lovins, see http://www.natcap.org
They figure we can reduce our GHG emissions by more than half cost-effectively, even by 75% or more. And I heard Hunter lovins say something like, “The poor cannot afford not to become energy efficient & conservative” & “The national energy policy comes down to the cracks around our windows.”

There are also some other hidden savings in “doing the right thing” — the EC (environmentally correct) thing. For instance, offsetting some driving with walking & cycling, and eating lower on the food chain could improve health & lower medical bills.

So re your questions “What will lead to better management of land use, and what will lead to less impact from livestock?” Eating less meat! Which is also good for the health. And when you consider that many toxins bioaccummulate up the food chain (toxins on plants get more concentrated in livestock, and still more concentrated in people who eat the livestock), well, there’s even more reason to reduce meat consumption. Going green is a win-win-win-win situation. Not doing so is a lose-lose-lose-lose situation.

Then people ask, if it makes sense to do all these things anyway (without considering global warming), then why haven’t they done them already? The answer may be that economists are wrong about man being rational and maximizing. Maybe there’s something disturbing and perhaps Freudian going on deep in our psyches — some thanatos death wish. Or, we’re just crazy.

Most of the observations seem to be based on changes in insolation (such as volcanic dimming). How do we know that sensitivity in C/(W/m2) is the same for GHG forcing as for insolation forcing?

The two sources of forcing have different ‘fingerprints’ and cause different distributions (vertically and geographicly) of temperature change. How do we know that those distributions do not cause different feedback effects?

[Response: They do – slightly. Read this paper for a full discussion of the issue. The bottom line is that the concept works pretty well for almost all forcings (otherwise we wouldn’t use it). You can use the simple model discussed before to show why it works in the simplest case. – gavin]

Re # 15 Eli,
I don’t understand your comment. I was responding to Vern’s (#4) request that Gavin to savage any conclusion in the IPCC report that is not based on incontrovertible evidence. How do you interpret that request?
Bet on what? I’m quite familiar with the major evidence for AGW, and I’ve learned from this site the serious flaws in Gray’s and Lindzen’s arguments.
Perhaps you misread my comment, or Vern’s?

This is a bit off topic, but does anyone have recommendations for a good, general book (for the “educated layman”) covering the science of global warming? I read and enjoyed “Field Notes From a Catastrophe” but it left me wanting more.

Intresting discussion regarding global cooling in the 60’s, 70’s. It gets quite emotional. Key reasons it didn’t become a scientific concensus are (i) that the trend didn’t last long enough for the hysgteria to set in and (ii) that an international body to study the issue was not established. The concern for global warming started in a similar way. People watched the trend for a few years and started to make a few noises about it, some media stories. One or two well-known scientists made some strong statements. The IPCC was formed and the snowball started to role. It will role until the its realised we are no longer in a rising trend. What I am sure about is that when we move again into a cooling trend, no AGW advocates of today will admit any error. What will be blamed is aerosols and that this other form of man-made pollution is taking over – and so it will still be our fault. You heard it here first.

[Response: Sadly no, I didn’t hear it first here, its been said many times before. For GC, you can look at http://en.wikipedia.org/wiki/Global_cooling . The key reason it didn’t become a sci cons was that the science didn’t support it – William]

#36 Alastair, I was around in the 70’s, and I must say that it didn’t feel like a cooling then, but now all over the world there is a warming felt by billions. The difference: it was a media prediction (perhaps inspired by Milankovitch theory) compared to the media reacting with no shortage of people in awe of deadly heat waves “la canicule 2003” , not having any winter in Europe amongst other myriad warming stories, many not heard from every place on Earth. The IPCC meets from common knowledge created by temperature change.

As a non-scientist I look forward to your step by step progression through IPCC report. I also appreciate the comment entries.
Several years ago,
I bought a copy of Natural Capitalism by Hawkins and Lovins. GREAT BOOK!

#57: “This is a bit off topic, but does anyone have recommendations for a good, general book (for the “educated layman”)”

Try Global Warming : The Complete Briefing by John Houghton. It is intended for a nontechnical audience and is detailed and thorough. You can check out the table of contents and some sample pages via the above amazon link.

The issue of how sensitive climate is appears to be the real issue in regards to how far humankind should go in mtigating carbon release into the atmosphere. Lubos Motl (who is probably well known to real climate and tends to have an opinion on anything that is controversial in science) writes this blog http://motls.blogspot.com/2006/05/climate-sensitivity-and-editorial.html on the subject and quotes well known climate detractors like Lindzen at MIT.

He agrees that there cannot be a runaway effect but he then takes the posiiton that the current 1.5 to 4.5 IPCC projections of temperature are incorrect citing the fact that 560 ppmv would mean no more than 1.5 C of warming through CO2 alone. So what is the issue here, I know from realclimate that he must be incorrect but I am no mathematician and hence I cannot vouch for his equation or his conclusions he draws from it (although I do know that the formual is exponential in nature and that we get more warming from the early CO2 increase than we do for even more) so he could be right for all I really know.

So what can I say that might reveal his depection: Is he only using CO2 and not greenhouse gases? Has he taken into account the albedo and aerosols to ?

Can realclimate answer this one for me please. Is he being economical with the truth or disengenuous to science and hence scientists?

I was disappointed that Eric shut down the discussion on the carbon cycle just as I was about to post. My question relates to just how well we understand the carbon cycle actually. I have reviewed the Wikipedia entry on this topic (I know, I should read the literature) and remain unsatisfied. For example, the Wikipedia entry fails, so far as I can see, to consider the impact of rising atmospheric CO2 levels on the biomass. We know that rising CO2 levels will stimulate plant growth. In effect, that sequesters CO2 in vegetative matter, and in a fashion that increases the biomass as atmospheric CO2 levels increase.

There may well be other aspects of the cycle that are poorly understood. For example, I seriously doubt that we really understand the CO2 issues with the ocean.

So my question in regard to the CO2 cycle is – just what level of confidence do we put on our understanding of the CO2 cycle. IPCC, Algore, RC and Hockey Team all suggest that we have a very clear understanding of this (Very Likely probably), but I seriously don’t see how this conclusion can be substantiated.

I have a question about arctic sea ice that I’ve yet to see addressed, and it won’t get out of my brain and just leave me alone —

While it’s true that sea ice lowers the albedo of the arctic region, we’re talking about a region that is a net heat loser on an annual basis. I’m not caffinated well enough this morning to calculate the annual watt-hours per square meter received at the north pole, but I’m guessing it isn’t a big number.

How does heat loss in the north polar region change with and without sea ice cover?

Re #48, having struggled through the simple model article recently, maybe I can clarify. If you double CO2 today, then forcing is 3.7W/m^2. However, as the atmosphere warms, other things change. For example, warmer air holds more water vapour which adds more forcing.

Both observations (of a more than 0.6C rise with only 380ppm CO2 level), and models show that the net effect of feedbacks is positive.

Hope I’ve got that about right.

One thing that really confused me till I got my head around it was the way papers talk about forcing (W/m^2/K) and then slip smoothly into sensitivity C/(W/m2) once they start talking about feedbacks.

Jamie and Alastair and PHE, your eagerness to abandon the conservation of energy tells me you don’t have much scientific background. The energy of a system–such as climate–does not change without something changing it. In the 1970s, yes, there were some observations of cooling, and even at the time, many researchers understood the cause to be blocking of sunlight by aerosols from the burning of fossil fuels. By the late 1990s the climate models had evolved sufficiently that this could be demonstrated. So, not only did scientists understand the cause of warming from the start of the industrial revolution into the early 1900s, they also understood the cause of the cooling observed from ~1940 to ~1975, and when emissions were controled, the warming re-emerged. Rather than undermining the credibility of climate science, this confirms it.
Your assertion that climate can change as a result of a “natural cycle” is as unscientific as the claim of a creationist that “GODDIDIT” unless you have some hypothesis as to what the forcing function of that “natural cycle” may be. Science works. Learn some of it.

Trend analysis of GISTEMP data from 1940 to 1975 indicates a temperature change rate of -0.15 +/- 0.25 deg.C/century. Note the error range is larger than the value, so the indicated trend is not statistically signficant.

The only real “global cooling” is from 1944 to 1951. Seven years. That’s all, folks. For the remaining period in question, from 1951 to 1975, the indicated trend is +0.07 +/- 0.5 deg.C/century. This indicates warming, not cooling, although again the trend is not statistically significant.

Just a quick question. Why wasn’t this released in February along with the summary? I know of no other field where a summary document is released months before the paper that it is supposed to summarize.

The “global cooling” talked about in a couple of glossy magazines (And Rob Reiner. We can’t forget his pivotal role.) was about the fact that we were in an interglacial period which could end. Which is true: interglacial periods do end. Since we had fairly bitter winters from 76-77 through 78-79, there was the spice of memory added to the mix.

Trevor, CO2 stimulates plant growth only to the extent that there are no other limiting factors. I believe Hank posted on this several posts back. The short answer is that it’s mixed. Some plants do better and some do worse. As I recall, weeds thrive. So, yes, this has been looked at.
The other misunderstanding reflected by your post is that unless the plant growth involved is dominated by long-lived woody plants, there isn’t much increase in long-term sequestration of carbon. Indeed, as the plants die and decay, a lot of the carbon goes back into the system as CH4, and so actually increases greenhouse efficiency. This straw has been grasped at repeatedly, and hasn’t supplied much bouyancy so far.

You’ll need to visit a library, talk to the reference desk, and borrow most of the journals; the abstracts will get you started.

Example:
“Conclusions drawn from experimental works differ when the data are grouped in a way such that the relative frequency of test conditions does not determine the emerging trends, for instance unrealistically strong CO2-‘fertilization’ effects, which are in conflict with some basic ecological principles. I suggest separating three test conditions: uncoupled systems (plants not depending in a natural nutrient cycle) (I); expanding systems, in which plants are given ample space and time to explore otherwise limited resources (II); and fully coupled systems in which the natural nutrient cycling governs growth at steady-state leaf area index (LAI) and fine root renewal (III). Data for 10 type III experiments yield rather moderate effects of elevated CO2 on plant biomass production, if any. In steady-state grassland, the effects are water-related; in closed tree stands, initial effects decline rapidly with time. Plant-soil coupling (soil conditions) deserves far greater attention than plant-atmosphere coupling (CO2 enrichment technology).”

A modest suggestion. Hank Roberts (whom I’ve learned a great deal from) often asks posters where they are getting their information about climate–especially when that information appears suspect. It occurs to me that it might be helpful in general if posters shared their sources of information–particularly the reliable ones, along with any biases they have observed. Realclimate remains my main source of scientific information about climate change. It is a goldmine. However, I also follow releases from NASA, NOAA and other sources. I do try to look at the IPCC reports, but I’m afraid that the politics here have a tendency to try to dilute the science (though in quite the opposite direction that the denialists imply). I try to flip through the stack of Science and Nature that accumulate over time. Unfortunately, I rarely make it to the library to read GRL anymore. Popular sources I use are Yahoo news. And I find the comments on the blogs at Scientific American an excellent source on the most popular denialist arguments of the day. I also try to keep in touch with colleagues at Physics Today, who actually still get to read this stuff as part of their day jobs. Nothing too novel or helpful, I’m afraid. But it’s a start.

Re: 43 “Seabrook NH is more recent than that (completed late 80s or early 90s I believe) and United Illuminating Customers in Connecticut are still paying it off.”

Even more current, look at the truly huge overrun costs for Ontario Hydro’s Darlington plant on Lake Onatrio. For overruns on overhaul costs check for Ont Hydro’s Pickering plant, also on L. Ontario. The Bruce plant (on L. Huron) is currently being overhauled, but by a private firm, so figures will not likely be available.

Just because a climate sceptics and trolls say that there was cooling from the 40s to the 70s does not mean that is not true. You only have to look at http://www.cru.uea.ac.uk/cru/info/warming/ to see that. Moreover, there were worries by reputable scientists that a rapid cooling could happen, See G.J. Kukla & R.K. Matthews, Science, 178, 190-1, 1972. Moreover, they were worried enough for it to reach the press, and for a letter to be penned to the President of the USA.

Of course the worries now are far greater than those then, but it is wrong to deny that they existed. One might accuse those deniers of being dishonest, but it is clear to me now that it is their firm belief in the infallibility of scientists that is leading them astray, and that they find it difficult to accept that scientists could ever have been wrong.

The problem is that they also believe that they too are infallible. When they are told the Arctic ice may be gone within 10 years, and as Jim Crabtree says “… the Arctic is our thermostat for the northern hemisphere. Once it is broken, we had better hang on for a wild ride” they are not afraid. For them, the IPCC consensus says that the ice will last until 2070 so that must be true.

If even the scientist cannot face up to the facts, then what hope is there for the rest of us?

During the last 10,000 years climate has been seesawing between the North and South Atlantic Oceans. As revealed by findings presented by Quaternary scientists at Lund University, Sweden, cold periods in the north have corresponded to warmth in the south and vice verse. These results imply that Europe may face a slightly cooler future than predicted by IPCC, the Intergovernmental Panel on Climate Change.http://www.sciencedaily.com/releases/2007/04/070428170229.htm

Wish I could remember which paper I read several months ago where the average age of the sea ice in the Arctic is now less than 3 years old (memory fading with age). So apparently the ice is turning over a lot faster than originally thought.

Bryson and Dittberner (1977) explained that the cooling projected by their model was due to aerosols (small particles in the atmosphere) produced by the same combustion that caused the increase in CO2. However, because aerosols remain in the atmosphere only a short time compared to CO2, the results were not applicable for long-term climate change projections. This example of a prediction of global cooling is a classic illustration of the self-correcting nature of Earth science.

Aerosols have in fact masked the effects of global warming through “global dimming” during the latter part of the twentieth century. However, some of their effects (e.g., sulfates lowering the albedo of clouds) contribute to global warming. There have been a number of posts on the subject of “global dimming” here in the past. One of Real Climate’s guest posters (Beate Liepert) was involved in some of the earlier modeling of its affects, including how it affects the formation of clouds, how sulfates decrease the albedo of clouds, how such polution can reduce the solar energy we receive on cloudless days, and how aerosols resulted in observed reduction of sunlight from the 1961-1990.

Indeed. Look very closely at that graph. Look at the period 1951 to 1970. Does that look like cooling to you?

Rather than trust what it “looks like,” I ran the numbers. I’m a professional mathematician specializing in the statistical analysis of time series. The numbers say: no cooling 1951 to 1970, or 1951 to 1975, or 1940 to 1970, or 1940 to 1975. The only verifiable global cooling is from 1944 to 1951. Seven years. That’s all, folks.

Let’s all face the truth: global cooling from the 40s to the 70s is a myth.

Here is one angle I am interested in: the more temperate regions are experiencing warmer winters and fewer freezing nights which kill mosquitos. Consequently, mosquitos are having extended seasons, and mosquito-borne illnesses are moving to more temperate zones and are at risk of becoming endemic.

Incidently, there was a story a while back regarding the production of methane by plants. Real Climate had a couple of posts on it, first because it was puzzling, then because it got misrepresented in the press.

Every so often a scientific paper comes out that truly surprises. The results of Keppler et al in Nature this week is clearly one of those. They showed that a heretofore unrecognised process causes living plant material to emit methane (CH4, the second most important trace greenhouse gas), in quantities that appear to be very significant globally.

Turns out that we have learned a little more in this regard:

Fast-forward eighteen months. A group of Dutch researchers put the Max Planck team’s conclusions to the test by tracing radioactive carbon isotopes through plants. Their conclusion: “There is no evidence for substantial aerobic methane emission by terrestrial plants.”

Tamino wrote “The only verifiable global cooling is from 1944 to 1951.”

I apologize for adding scifi to the talk, but I was asked to ask you good people whether you think the Hiroshima/Nagasaki/above ground A-bomb tests might have generated enough airborne debris to contribute significantly to the cooling effect Tamino cited (and I suppose whether general wartime activity elevated fossil fuel use enough to accelerate post-war AGW some). This question I gather comes from musing about Dr. Sagan’s nuke winter idea. I also have been asked to say that the meaningful contributors to RC are simply brilliant :)

Re #65: Probably the key relationship to bear in mind regarding Arctic sea ice is that the heat absorption will be through the open water in the summer, but that winter sea ice will still develop and greatly reduce the amount of heat lost then. While summer insolation is obviously much less than farther south, it’s still large enough to do the job (although not by itself at present, since encroaching warm currents have been found to be a big part of it). Another aspect (IIRC) is that the persistence of the Arctic sea ice is related to the presence of a surface layer of relatively fresh water that will be progressively disrupted (by mixing) as the warming proceeds, so the summer ice-free state will itself acquire persistence as that layer dissipates. NSIDC has good non-technical explanations of all of this.

Ray Ladbury – In #67, you state that scientists now understand the effect of aerosols on global mean temperatures in the 20th century and that the current models confirm the credibility of climate science regarding this issue. The IPCC AR4 report does not appear to share your confidence, as shown in Table 2.11. For the four types of aerosols, the report indicates a level of scientific understanding ranging from low, to low to medium; along with a low grade of consensus.

In #71 you discuss stimulated plant growth and the lack of long-term sequestation of carbon that results from the increased growth. There is actually quite a bit of information to the contrary. The article below is a good place to start.

It is a pretty sobering assessment of the efforts of developed countries to reduce GHG emissions. Monbiot argues that even the most aggressive GHG reduction targets currently being proposed (e.g. by the EU, Britain and Sweden) fall short of what current science says will be needed to prevent “dangerous” global warming of 2 degrees Centigrade above pre-industrial levels.

B. Buckner, I couldn’t get your link to work, but I did spend some time poking around co2science. I recommend it to anybody who needs a good laugh. Must be nice having a job where all you have to do all day is cherrypick the latest studies that provide even minimal support to your position. Oh, and did I say support–Ex-Mob is providing a lot of it to co2science.org.
So, you think all we have to do is plant trees? Then I suppose you’re fine with Al Gore’s carbon offsets, right?
Yes CO2 does promote growth in some plants under some conditions. However, really long-term sequestration requires a continual increase in the amount of carbon stored in plants. Redwoods are a good carbon sink. Brussel sprouts (as anybody who has eaten them knows) are not. Short-lived plants die and decay, returning their carbon to the cycle fairly quickly, not just as CO2, but also a CH4–a more potent greenhouse gas. And long-lived trees grow slowly, and when they reach maturity, the growth stops. What is more, they stop growth under the canopy. So, while forests can act as carbon sinks, the potential is limited. And the assertion that CO2 is a benefit to agriculture is without merit–weeds like CO2 even more than crops do.

As to aerosols, yes, they remain an area of uncertainty. They are certain enough that we know that if you dump soot into the air, you get cooling (or at least a slowdown in warming). They are also certain enough to nail the effect of a volcanic eruption such as Mt. Pinatubo nuts on. In other words, they are certain enough that we know they won’t change the answer dramatically.

Recent studies looked at increased CO2 and other climate effects on plant growth. Remember, plants need more than CO2 and warmth to grow. Nitrogen and other nutrients in the soil, water levels, and light levels all play important roles. Merely increasing one or two of these factors may not give the expected results. For instance, increasing CO2 may not encourage the plants you would like to grow, but instead encourage “weeds.”

Also remember the rate at which this change is happening is faster than a natural climate shift rate, and desirable plants may not be able to move quickly enough. Also, the areas into which plants might migrate may not be suitable for their growth.

I thought of that idea a little over a year ago; it does seem quite a coincidence that 1945 marked the first A-bomb explosions and several were tested throughout the remainder of the 40s. So I investigated the number of above-ground nuclear explosions, and found that they continued throughout the 50s, but the nuclear test ban treaty reduced the number greatly in the 60s. If I recall correctly, the last above-ground test was in 1970. Global cooling doesn’t match this pattern.

Another idea is that the massive firestorms from conventional bombing late in world war II may have contributed to the global cooling 1944-1951. Moderators — any comments?

The Chinese have been doing studies where they vent rice in the field with CO2 which simulates projected levels from 2050. Rice grows more quickly, but has considerably diminished nutritional value. Additionally, the does not take into account the increased temperature (rice is especially sensative to heat) or the effects of drought.

These are radical, holistic re-visions of how we feel and behave toward Earth and how we relate to one another. They may seem too radical, in the sense of going to the roots of the problem, but the alternative is the Lovelockian Earth ridding itself of human pathogens, which is elegant as theory but mind-numbingly brutal in practice. At least let’s try to talk about some fundamental reformations in human society and relationships.

They have taken a legititmate scientific paper and selectively edited it so that you will think and act the way they want you to.

This is an old trick of theirs (and the left’s and the right’s as well on global warming) and it has helped stop any action on global warming/climate change for ten years….time that we might or might not have.

Read the original paper at your library or from the origional source and not what someone wants you to believe.

The Union of Concerned Scientists has this to say about the co2science.org website.

Thanks for the additional info. Still not the paper I was looking for. I will do some more searching in the next few days.

#92.

The drop in nutrition value is true for wheat and other grains when CO2 passes a certain point. I would have to find a reference, but one of the Universities found that the caterpillars would not go into pupae stage.

These are radical, holistic re-visions of how we feel and behave toward Earth and how we relate to one another…

Preamble: Our one and only planet is heating up, fast…4) De-throne the corporate rulers.

OK there…

Maybe before we get around to discussing your manifesto, we could cover the IPCC AR4 Report.

I was thinking, we all have topics that we might want to touch on, whether it happens to be how well the plants might do with increased carbon dioxide, the projected intensities of storms, the spread of diseases, global dimming, etc. But rather than trying to discuss all of these things all at once, maybe we could discuss them as they come up which covering the report.

In addition, rather than asking Gavin and the rest of the good people at Real Climate to play Cartesian doubt with it, maybe we can ask that they give their realistic assessments of it, or better yet, maybe let them figure out what they want to cover since they’ve got the degrees and seem to be pretty good at figuring that out all for themselves – and we can raise other points relevant to what is being discussed at the time. But in any case, I think going over the report chapter by chapter, as they intend, will provide the discussion with some structure – and it may even give us the chance to examine what the report actually states. Any critique can be done in relation to its actual content at the time that we are actually going over the relevant part. Then if we think there are other important topics which didn’t fit into the structured discussion, maybe we can turn to them at the end.

Well low and behold, section 7.3.2.2.3 of the IPCC AR4 Report “Residual Land Sink” cites the same paper and comes to the same conclusions as the misleading, laughable, PR advocacy, cherry picking, Exxon-Mobil funded, fossil fuel duping CO2Science site.

Rather than making ad hominem attacks on the authors, perhaps we can deal directly with the science involved.